Conventionally, door opening/closing devices for a vehicle, which include an actuator (a support member) that is telescopically driven in an axial direction between a periphery of an opening of a vehicle body side and a tailgate (a back door) provided at this opening to be openable/closable, and thereby opens/closes the tailgate, are known (e.g., see Japanese Unexamined Patent Application, First Publication No. 2014-100956).
This actuator includes a tubular first housing, a second housing which has a larger diameter than the first housing and in which the first housing is inserted, a motor that is provided inside the first housing, a screw spindle that is coupled to the motor via a speed reducer and is disposed coaxially with the motor, a spindle nut that is fixed to the second housing and is screwed on the screw spindle, and a compression coil spring that is housed in the second housing and biases the first housing and the second housing in a direction of extension. The motor and the speed reducer are separately provided inside the first housing. A bearing for rotatably supporting a rotary shaft of the motor is provided by applying a drawing process on a motor housing. On the other hand, the speed reducer is rotatably supported by the rotary shaft of the motor and the screw spindle.
With this constitution, when the actuator drives and rotates the motor, rotation of an output shaft of the motor is transmitted to the screw spindle via the speed reducer, and the screw spindle is rotated. Due to the rotation of the screw spindle, the spindle nut screwed on the screw spindle moves in an axial direction of the screw spindle. Thereby, the second housing is projected/retracted with respect to the first housing, and the actuator is expanded/contracted.